1. Field of the Invention
The present invention relates to electronic capacitive touch sensors on film substrates, and in particular to those which incorporate four color graphics and designs behind clear plastic protective films.
2. Description of the Prior Art
Mass produced products like toys are highly sensitive to component costs. So circuits and construction methods for making interactive toys must be very inexpensive to manufacture.
A conventional inexpensive toy electric guitar for children has been made from sheets of paper cut in the shape of a guitar with a body, neck, and headstock, then essentially a photograph of an attractive guitar is printed on top. The printed photograph shows all the details of wood grain, frets, strings, saddle, sound hole, pickups, bridge and adjusting knobs. On the backside, a plastic film with printed circuits for touch pads is glued on using adhesives. This assembly is then fitted to a thick plastic body frame for support, and a pigtail from the printed circuits for the touch pads is plugged into an amplifier module.
The downside with this type of construction is the paper and adhesives can constitute the major component costs. And printing photographs on the outside on top of paper makes it very vulnerable to user wear and the environment. Such color printings on paper also tend to produce poor quality results, the lines and details are not sharp and crisp.
Subassemblies of capacitive touch sensors are very often manufactured in places in the world that have high humidity, and the shipping containers they are sent in can be dripping-wet inside. Paper based products do not survive well in these conditions, and metal based conductive inks tend to corrode and fail. So better alternatives with passivation coatings and protective finishes need to be supplied.
A few commercial products have used graphics printed on plastic, but they assemble their electronic capacitive touch sensors separately behind the graphic sheets. Such types of construction add to the costs and increase problems with reliability and service life. The manufacturing costs associated with mass produced consumer electronics are often the number one consideration behind functionality, and saving just a few cents per items can translate to millions of dollars in increased sales and profits.
What is needed is a thin, but rugged, capacitive touch sensor that is more attractive and less expensive to mass produce than conventional devices.